dbx 122 - Page 11

10
DETAILED
OPERATING
INSTRUCTIONS
GENERAL NOTES
Level and Impedance
The 122 and 124 input levels, output levels and
impedances are designed for compatibility with most
hi-fi and semi-pro equipment. Because the dbx 122 and
124 input impedance is 50k-ohms, the units can be driven
from high or low impedance sources. The dbx inputs also
will accept a wide range of voltages. The dbx outputs will
drive up to 7 volts into ioads of 5000-ahms or greater.
This
means
that
you
can
connect
the
122
or
124
output
to
almost
any
type
of
equipment
found
in
a
normal
hi-fi
or
semi-pro
system.
However,
thé
dbx
122
and
124
are
not
meant
for
professional
levels
of
+4dBm
(1.23V)
to
+8d8m
{1.95V), nor are they meant for driving low impedances,
such
as
600-ohm
professional
inputs.
Use
the
dbx
150
semi-
professional series or any of the dbx professional series
units for these applications.
Grounding
The 122 and 124 are not grounded to the power mains
through their power cords. They obtain a ground via the
shields of the interconnecting audio cables from the pre-
amplifier, receiver, and/or from the tape machine. No
special ground wires need be connected between the dbx
chassis and any other equipment. If you hear hum, try
reversing the AC plug, and if that does not help, check to
make sure all audio cables are properly installed and that
there are not broken conductors in any cable. Hum and
radio station pickup are sometimes caused by microscopic
dirt particles on the mating surfaces between the chassis
and cable connectors, so clean these areas periodically.
Cable Length
Some installations will tolerate longer cables, but when-
ever possible it is a good idea to keep signal cable runs
under 10 feet. This minimizes hum and noise pickup, and
also
helps
prevent
high
frequency
losses
naturally
caused
by cable capacitance.
dbx and Dolhy®* Together
The
dbx
{[
tape
noise
reduction
system
provides
at
least
20dB
more
noise
reduction
than
Dolby
"B”
tape
noise
reduction
systems,
and
15dB
mare
than
Dolby
“A,”
so
there
is
no
need
to
use
Dolby
processing.
If
your
tape
machine
has
internal
Dolby
processing,
switch
it
Off
and-
use
only
the
dbx
1
encoding
and
decoding.
Dolby
encoded
tapes
are
not
compatible
with
dbx
||
decoding
(and
vice-
versa);
if
a
tape
was
recorded
with
Dolby
encoding,
it
must
be Dolby
decoded.
NOTE:
While
it
is
possible
to
combine
both
dbx
I!
and
Dolby
processing,
we
do
not
recommend
it
because
any
imperfections
in
the
Dolby
encode/decode
processing
will
be
magnified
by
dbx
II
treatment.
Since
dbx
II
processing
alone
reduces
noise
to
inaudibility,
there
is
really
no
need
to
use
dbx
II
with
another
tape
noise
reduction
system.
*'Dolby’ is a trademark of Dolby® Laboratories Inc.